A vacuum-assisted, countergravity casting apparatus using a gas permeable mold is described in the Chandley et al U.S. Pat. No. 4,340,108 issued Jul. 20, 1982 and U.S. Pat. No. 4,606396 issued Aug. 19, 1986. Typically, the casting apparatus includes a casting mold having a porous, gas permeable upper mold member (cope) and a lower mold member (drag) sealingly secured together at a common horizontal parting plane, a vacuum box confronting the gas permeable upper mold member and means for immersing the underside of the lower mold member in an underlying pool of melt (e.g., molten metal) while evacuating the vacuum box to draw the melt upwardly through one or more ingate passages in the lower mold member into one or more mold cavities formed between the upper and lower mold members. Typically, the upper and lower mold members comprise gas permeable, resin-bonded sand mold members which are self-supporting and adhesively secured (glued) together at the common horizontal parting plane to minimize leakage of the melt at the parting plane.
The casting mold and the vacuum box are sealed together using a gasket seal compressed between the bottom lip of the vacuum box and an upwardly facing sealing surface or flange on the upper or lower mold member. Various mechanical clamping arrangements have been provided for clamping the vacuum box and the mold together to compress the seal therebetween; for example, as shown in U.S. Pat. Nos. 4,340,108; 4,616,691; 4,632,171 and 4,658,880. In these clamping arrangements, the casting mold typically includes a plurality of relatively complex structural attachment features, such as threaded lugs, threaded bores, slotted keyways and the like, for engagement with the clamping mechanism. The attachment features provide multiple pick-up locations on the mold for engagement with the clamping mechanism in a manner that oftentimes produces considerable local stresses on the mold at these locations, especially when relatively large, heavy molds are used. To this end, the size of the casting mold is sometimes limited to reduce mold weight and stresses imposed on the mold at the pick-up locations. Moreover, the clamping mechanism oftentimes engages the casting mold at pick-up locations disposed in such proximity to the mold underside as to subject the clamping mechanism to accidental and detrimental immersion in the melt during countergravity casting.
It is an object of this invention to provide a unique countergravity casting apparatus including a casting mold having relatively simple, pick-up features on the mold sides for engagement by a mold pick-up mechanism in a manner to uniformly distribute pick-up stresses over a large area of the mold and in a manner to provide a large mold immersion zone between the mold underside and the mold pick-up mechanism.
It is another object of this invention to provide a unique countergravity casting apparatus including a casting mold having pick-up features thereon in a generally level orientation and a mold pick-up mechanism for engaging the mold pick-up features in a manner that accommodates any unevenness in the mold pick-up features or unparallelism between the pick-up features and pick-up mechanism.
The aforementioned objects and advantages of the present invention will become more readily apparent from the following detailed description and drawings.